One aspect of metal cutting research is primarily concerned with the activity occurring between the cutting edge of a tool and the workpiece. For example, it is often necessary to study the zone in which the metal chip is sheared from the remainder of the workpiece, i.e. the zone of contact between the cutting tool and the chip root. To permit this research, it is necessary to effectively freeze the cutting action without substantially disturbing the state of the chip. The chip root can then accurately be studied for various phenomena, such as the plastic deformation that occurs with chip separation.
A variety of quick stop devices are used to abruptly interrupt the cutting process. Those devices abruptly change the relative velocity between the cutting tool and the cutting surface to zero to preserve the workpiece chip formation as accurately as possible. This can be achieved by either accelerating the tool out of the cutting area and away from the workpiece (or conversely, accelerating the workpiece out of the cutting area and away from the tool) or abruptly accelerating the workpiece with the tool remaining in contact.
Existing quick stop devices provide rapid changes in relative velocity according to several different methods. In one method, a cutting tool is moved along a workpiece held by a shear pin. At a predetermined time, an explosive material is ignited and the forces generated break the shear pin and abruptly drive the cutting tool away from the workpiece.
Other devices combine the cutting force with a spring force to quickly move the tool away from the workpiece during cutting. This method, however, is subject to the relatively small cutting and spring forces, often rendering insufficient acceleration of the tool relative to the workpiece. Some devices simply break the cutting tool, either mechanically or by using the force of an explosion to force a hammer against the tool. The force breaks the tool and moves it away from the cutting area.
Problems with existing devices include the relatively long time required and the difficulty involved with setting up the devices for experimentation. This is particularly true for ballistic or explosive quick stop designs. It is also difficult to adapt existing designs to a variety of different cutting machines, e.g. various machine tools. At the same time, it may be desirable to use the quick stop devices with a variety of different machine tools that can, for instance, accommodate varying sizes of cutters.
Some existing quick stop devices work adequately for examining the metallurgical configuration of a longitudinal cut along a workpiece. However, the devices are inadequate for investigating the cutting of a workpiece by a drill bit in which the cutting takes place along a circular interior surface.
The present invention addresses the various drawbacks of existing quick stop devices.